Motorcycle engines with two banks are generally mounted to the motorcycle frame with their crankshaft axis arranged laterally of the forward direction, and with one bank of cylinders located forwardly of the other. In such installations, it is a simple matter to locate the exhaust pipe or pipes from the forward bank so it is not readily contacted by the rider. However, placing of the exhaust pipe or pipes from the rear bank presents difficult problems. Because of the engine construction, if the rear bank pipes are directly connected with the front bank pipes at the side of the engine, there is risk of contact by the leg of the rider. If they extend directly rearward, the risk exists that their heat may deteriorate the rear tire.
Furthermore, in V-type engines with four cylinders, there is an advantage if all of the pipes can be the same length.
It is an object of this invention to locate the rear exhaust pipes in a location not threatening to the rider or to the rear tire.
It is another object of this invention to enable the four exhaust pipes to be made the same length.
This invention is carried out with a motorcycle frame which includes a forward section which carries an engine and a front wheel, and a fork-like rear section which is pivoted to the forward section and carries the rear wheel, and a transmission from the engine to the rear wheel. The engine has two banks, the cylinder or cylinders of the front bank being forwardly of the cylinder or cylinders of the rear bank. The forward exhaust pipe or pipes extends forwardly, downwardly and outwardly, and then rearwardly beneath the side of the engine. In one embodiment of the invention, the rear exhaust pipe or pipes extends rearwardly and downwardly between the engine and the pivot axis of the arms of the rear section between the planes of the arms. All pipes communicate with a muffler, and the muffler exhausts to atmosphere.
In another embodiment of the invention, in which a V-type four cylinder engine is used, the rear pipes cross one another, and descend outside of the planes of the arms and forward of the pivot axis of the arms to enter the muffler, and extend in the muffler for such a length that the lengths of all pipes are equal.